Foam inhibited gear lubricant composition



United States Patent 3,033,789 FOAM INHIBITED GEAR LUBRICANT COMPOSITION Peter A. Asself, Cleveland, Ohio, assignor to The Lnbrizol Corporation, Wicklifie, Ohio, a corporation of Ohio No Drawing. Filed Mar. 28, 1957, Ser. No. 649,017 5 Claims. (Cl. 252-493) This invention relates to the foaming of mineral lubricants and in a more particular sense to the prevention or destruction of foam in such mineral lubricants.

The formation of foam or froth in a hydrocarbon lubricant is occasioned at least in part by the vigorous agitation of mixtures of air and the lubricant which inevitably occur in any effective system of liquid lubrication. Thus, in the lubrication of an internal combustion engine, whether it depends upon a pump or is effected by splash, the lubricant is vigorously agitated with air to such a degree as to provide a very favorable environment for the formation of foam. The case is much the same for gear lubricants where the lubrication involves an obvious violent agitation of the oil. In addition to the role which agitation plays in causing foam, the presence of one or more additives in present day lubricants is a second factor which aids in the formation of foam. Such additives generally are quite polar and tend to increase the surface tension of the oil in which they are dissolved. This condition of increased surface tension enhances the tendency to foam.

The objection to foam in a hydrocarbon lubricant arises primarily from the fact that appreciable quantities of lubricant may be lost by overflow through breather or vent outlets. Such breather outlets are present in a crankcase for the purpose of allowing the escape of blowby gases from the combustion chambers. Many axlehousing units likewise contain such breathing vents, and

in such units which do not contain a vent the problem of oil depletion is replaced by the problem of oil working its way past the seals and into brake drums, etc.

It will be seen that these problems are the result of the effective increase, by foam and froth, of the volume of a lubricant above that which the crankcase or other reservoir is intended to accommodate. Inasmuch as the stability of foam is enhanced by increased viscosity the problem is more acute in gear lubricants than in other less viscous lubricants.

In many cases the foaming of a hydrocarbon solution or dispersion can be dissipated effectively by incorporation in the liquid of a small amount of a liquid polymeric dialkyl silicone. Such polymeric silicones are commercially available and are effective in remarkably small concentrations, viz., one to ten parts per million. In other cases, however, the use of a polymeric silicone does not aiford a completely satisfactory solution of a foaming problem. Such a case is exemplified by a lubricant which provides an acidic environment. In such an environment the effectiveness of the polymeric silicone as an anti-foam agent is gradually diminished until after a week or two its effectiveness is almost nil.

It is accordingly a principal object of the present invention to provide a relatively permanent foam-free lubricant.

Another object of this invention is to stabilize the antifoam properties of polymeric dialkyl silicones in particular environments.

These and other objects are accomplished by the com- 3,033,789 Patented May 8, 1962 position of the present invention, which composition comprises in combination a mineral lubricating oil, a liquid polymeric dialkyl silicone, and an amine. This composition is an effective anti-foam material not only in neutral and basic media, but also in acidic media. Furthermore, the effectiveness persists through a much longer period of time than has previously been possible in acidic media.

A description of polymeric silicones which may be used in the hereindescribed composition is included in US. Patents 2,416,503 and 2,416,504. They include principally the liquid polymerization products of the low molecular weight dialkyl silane diols. These materials, although quite insoluble in hydrocarbon liquids, are readily dispersible therein, and are thought to be elfective by virtue of their low interfacial tension toward hydrocarbon liquids. Dispersions of these liquid polymeric products are quite stable and effective as an anti'foam agent, even in the presence of a great number of types of other additives.

Either aliphatic or aromatic amines may be used in combination with the above-described silicones. Specific examples of suitable amines include ethyl, butyl, hexyl, octyl, decyl, dodecyl, octadecyl, etc. amines, and pyridine, quinoline, aniline and N-substituted anilines, etc. Secondary and tertiary amines, as well as primary amines, are within the contemplated scope of the invention, and such specific amines as triamyl, diamyl, diisopropyl, etc. amines have been found to be satisfactory for use in the anti-foam compositions described herein.

As indicated previously the combination in a lubricant of a polymeric silicone and an amine is an elfective antifoam agent not only in neutral and basic media, but likewise is satifactorily eifective in acidic media. This is of especial significance in the field of gear lubrication, because many gear lubricant additives depend upon their acidic character for extreme pressure properties. Thus many gear lubricant additives are sufiiciently acidic to impart an acidic environment throughout the lubricant in which they are employed, even though they be used only in relatively minute proportions. Furthermore, the quality and desirability of acidic additives of this type are such that a satisfactory gear lubricant for present day use may often require the presence of such an additive.

This fact, i.e., the presence in many present day gear lubricants of an acidic environment, plus the previously noted facts (1) that the polymeric silicones by themselves are not so effective as anti-foam agents in acidic media and (2) that the stability of foam is enhanced by increased viscosity, points up a critical situation which preceded the discovery of the composition of this invention.

The acidic gear lubricant additives which may be used in present day lubricants include among others the acidic product obtained by hydrolysis of the reaction product of an alcohol and a phosphorus halide. Usually in such an instance the phosphorus halide is a phosphorus chloride, e.g. phosphorus trichloride, thiophosphoryl chloride, etc. Such acidic products are phosphites and phosphates, including the thio derivatives thereof. The particular acidic lubricants contemplated in this invention are those which contain such phosphorus products in concentrations ranging from about 0.05 to about 1.0%. In lubricants which contain such acidic materials the anti-foam activity of a silicone additive is slowly diminished until after a week or two it is almost completely dissipated. This phenomenon is illustrated by the observation that a gear lubricant which contained 0.1% of an acidic phosphite prepared by the reaction of 2.5 moles of Z-methylpentanol- 4 with 1 mole of phosphorus trichloride followed by hydrolysis of the resulting product, and 0.004% of a liquid dimethyl silicone polymer prepared by the condensation of dimethyl-silane diol, and having a molecular weight of 25,000, showed no foam immediately after it was prepared, but after it had been stored at 150 F. for one week it showed 280 ml. of foam. The foam was measured by the following procedure, taken for A.S.T.M. test D-89246T:

A 180-ml. sample is placed in a 1000-ml. graduated cylinder and heated rapidly to 200i F., then placed in a bath maintained at 200:1F. When the oil sample reaches the bath temperature a current of air is bubbled through the sample at the rate of 94:5 ml. per minute for five minutes. The volume, in ml., of air foam then is measured immediately and recorded.

The same gear lubricant, containing an acidic phosphite and 0.004% of a dimethyl silicone polymer as described above, showed an even greater volume of foam, 470 ml., after it had been stored at 150 F. for a second Week. Inasmuch as a gear lubricant is employed under conditions in which the temperature reached often exceeds 150 F. it is apparent that this lubricant is quite unsatisfactory beyond the first week of use, with respect to its foaming tendencies.

A considerably greater degree of permanence of antifoam activity is available from the use of the composition of this invention. This is indicated by the tabulated data shown below:

Volume of Foam observed after storage at 150 F. for:

Lubricant 2 wks. 3 wks. 4 wks.

H OOOOOUIO H OOQUIQO OOOOOO As has been indicated earlier in this description the polymeric alkyl silicones are effective in extremely low concentrations. For the purposes of this invention it is in certain instances suflicient that as little as one part per million (0.001%) of an alkyl silicone polymer be used. The amine likewise is effective in quite low concentrations and the scope of the invention is to be construed as covering the use of amounts of amines of the order of at least about 0.05%. These minimum figures are expressed numerically as percentages by weight of the final lubricant.

4 I The utility of lesser amounts of silicone polymer is demonstrated by the following data:

Lubricant 1 wk. 2 wks. 3 wks. 4 wks.

A1=SAE lubricant containing an acidic phosphite and 0.001% of a dirnethyl silicone polymer (as described above).

B 1=A +0.3% of dehydroabietyl amine.

C1=SAE 90 lubricant containing an acidic phosphite prepared by the reaction of 2.5 moles of methylcyclohexyl alcohol with 1 mole of phosphorus trichloride followed by hydrolysis of the resulting product, 0.002% of a liquid dimethyl silane polymer prepared by the condensation of dimethyl-silane diol, and havin a molecular weight of 25,000, and 0.15% of N-octadecyl trlmethylene amine mono-oleate.

D 1=A 4-01% of tert-octyl amine.

E =A +0.15% of dodecyl amine.

F 1=A +0.15% of diisoamyl amine.

G =A +0.1% of n-octyl amine.

As is the case with virtually all lubricant additives, the novel composition described herein is handled most conveniently as a concentrate. This facilitates its storage and transportation difiiculties, and also allows its ready incorporation into a final lubricant. In such instances it is particularly convenient to have the silicone polymer present in concentrations as high as 0.1% and the amine in concentrations up to two or three percent or more.

Other modes of applying the principle of this invention may be employed, change being made as regards the details described provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A relatively non-foaming gear lubricant comprising in combination a major proportion of a mineral lubricating oil, from about one to a thousand parts per million of a liquid polymerized low molecular weight dialkyl silicone, from about 0.05 to about 3.0% of an oil-soluble, hydrocarbyl amine, and from about 0.05 to about 1.0% of an acidic alkyl phosphite selected from the group consisting of lower alkyl and alkyl-cycloalkyl phosphites.

2. The gear lubricant composition of claim 1 characterized further in that the amine is an alkyl amine.

3. The gear lubricant composition of claim 1 characterized further in that the amine is a primary amine.

4. The gear lubricant composition of claim 1 characterized further in that the amine is tertiary octyl amine.

5. The gear lubricant composition of claim 1 characterized further in that the amine is diisoamyl amine.

References Cited in the file of this patent UNITED STATES PATENTS 2,151,300 Moran et al. Mar. 21, 1939 2,375,007 Larsen May 1, 1945 2,397,377 Smith May 26, 1946 2,498,628 Cyphers Feb. 28, 1950 2,563,588 Dixon Aug. 7, 1951 2,773,032 Cantrell Dec. 4, 1956 

1. A RELATIVELY NON-FOAMING GEAR LUBRICANT COMPRISING IN COMBINATION A MAJOR PROPORTION OF A MINERAL LUBRICATING OIL, FROM ABOUT ONE TO A THOUSAND PARTS PER MILLION OF A LIQUID POLYMERIZED LOW MOLECULAR WEIGHT DIALKYL SILICONE, FROM ABOUT 0.05 TO ABOUT 3.0% OF AN OIL-SOLUBLE, HYDROCARBYL AMINE, AND FROM ABOUT 0.05 TO ABOUT 1.0% OF AN ACIDIC ALKYL PHOSPHITE SELECTED FROM THE GROUP CONSISTING OF LOWER ALKYL AND ALKYL-CYCLOALKYL PHOSPHITES. 